The present invention relates to shaped bodies and sheets comprised of gelatin or of which the outer layer is comprised of at least 5% gelatin or chemically modified gelatin. More particularly, the present invention relates to hard and soft gelatin capsules and sheet gelatin, which has been printed by using the ink jet process, and to processes for printing these shaped bodies and sheets. Still more particularly, the present invention relates to the inks used in the process of imprinting these shaped bodies and sheets.
Shaped bodies comprised of gelatin or having outer layers comprised of gelatin often need to be printed with an identifying logo, code or other mark. For instance, such a mark might identify the manufacturer or a brand name, or it might provide other useful information. Existing printing methods include embossed printing, gravure printing, screen printing, laser printing and, more particularly and frequently in the case of gelatin capsules, ink jet printing. The increasing frequency of the use of ink jet printing on gelatin capsules is due to the fact that printing techniques other than ink jet printing require the application of a mechanical and/or thermal load which may damage the capsules. A further drawback of existing printing methods is the undesirable occurrence of staining spots and streaks that may be caused upon contact with the freshly printed capsules after they leave the printing station. The ink jet printing process is especially preferred for gelatin capsules because it enables printing without contact and thus avoids damage to the product. Specifically, printing rollers and rubber rolls are no longer required. Further, the ink jet process allows rounded articles such as, for example, gelatin capsules filled with bathing oils, to be provided with larger imprints, even though the surfaces of the articles are greatly curved.
The inks that have been used for ink jet printing of hard and soft gelatin capsules consist predominantly of water. Further, they contain additional solvents such as, for example, ethanol, isopropanol and propylene glycol and viscosity-increasing polymers such as, for example, cellulose derivatives. In addition, the colorants most frequently used are readily water-soluble organic dyes.
As disclosed by Derwent's abridged edition 86-090677/14 of JP 61-035-989-A, an ink jet process is known, wherein the ink-bearing material such as gelatin, casein, starch, gum arabic, sodium alginate, poly(acrylic amide), PVP, poylurethane, CMC, or polyester is coated with an ink-permeable layer of a somewhat less hydrophilic material such as poly(vinyl acetate), polyethylene or PVC. However, this process is completely unsuitable for printing gelatin capsules.
Further, as disclosed by DE-A-34 11 136, there exist thixotropic gravure printing inks having a resinous binder, pigment and a solvent system, wherein flowability is modified, for example, by aluminum salts of alkane carboxylic acids, most frequently in admixture with fatty acids and other ingredients. However, such inks are completely unsuitable for the ink jet process.
As suggested above, it has been discovered that one drawback inherent in the ink jet process is the fact that gelatin capsules, especially those having a capsule filling containing liquid hydrophilic components such as water, ethanol, propylene eglycol or poly(ethylene glycols), when stored adjacent to other capsules, may tend to transfer some ink jet ink to adjacent capsules. As an unfortunate result, so-called "ghost images" or staining spots and mirror-image portions of the typeface or design may appear on the adjacent capsules. Similar phenomena are also observed with gelatin sheets such as "sheet gelatin" which is used as a food product. Since printed sheets of gelatin are often closely stacked together in a package, the occurrence of "ghost images" is likely.
It is therefore an object of the present invention to provide a printed shaped body or sheet of gelatin without the above-discussed disadvantages.
It is a further object of the present invention to provide an improved ink jet printing process for printing shaped bodies or sheets, whereby the above-discussed disadvantages will be eliminated.
More particularly, it is an object of the present invention to provide a printed shaped gelatin body or sheet and an improved ink jet printing process for printing shaped gelatin bodies or sheets, whereby the ink deposited by the ink jet process remains durably and firmly adhered to those locations where it has been deposited, so that it cannot be inadvertently transferred to the adjacent surfaces of other shaped bodies or sheets.